Maintenance; Carburettor Adjustment - Jonsered CS2156 Operator's Manual

Carburettor adjustment

Due to existing environmental and emissions legislation your
chain saw is equipped with movement limiters on the
carburettor adjuster screws. These limit the adjustment
possibilities to a maximum of a 1/2 turn.
1/2
Your Jonsered product has been designed and manufactured
to specifications that reduce harmful exhaust fumes.
Function, Basic settings, Fine adjustment
WARNING! Do not start the chain saw unless
!
the bar, chain and clutch cover (chain brake)
are fitted, otherwise the clutch may come
loose and cause personal injury.
Function
• The carburettor governs the engine's speed via the
throttle control. Air and fuel are mixed in the carburettor.
The air/fuel mixture is adjustable. Correct adjustment is
essential to get the best performance from the machine.
• Adjusting the carburettor means that the engine is
adapted to local operating conditions, e.g. climate,
altitude, petrol and the type of 2-stroke oil.
• The carburettor has three adjustment controls:
- L = Low speed jet
- H = High speed jet
- T = Idle adjustment screw
L
T
• The L and H-jets are used to adjust the supply of fuel to
match the rate that air is admitted, which is controlled with
the throttle. If they are screwed clockwise the air/fuel ratio
becomes leaner (less fuel) and if they are turned anti-
clockwise the ratio becomes richer (more fuel). A lean
mixture gives a higher engine speed and a rich mixture
gives a lower engine speed.
• The T-screw regulates the throttle setting at idle speed. If
the T-screw is turned clockwise this gives a higher idle
speed; turning it anti-clockwise gives a lower idle speed.
30 –
English

MAINTENANCE

1/2
H
Basic settings and running in
The basic carburettor settings are adjusted during testing at
the factory. Avoid running at a too high speed during the first
10 hours.
CAUTION! If the chain rotates while idling the T-screw
must be turned anti-clockwise until the chain stops.
Rec. idle speed: 2700 rpm
WARNING! If the idle speed cannot be
!
adjusted so that the cutting attachment
stops, contact your dealer/service
workshop. Do not use the machine until it
has been correctly adjusted or repaired.
Fine adjustment
Contact your servicing dealer, if the idle speed setting cannot
be adjusted so that the chain stops. Do not use the chain saw
until it has been properly adjusted or repaired.
Changing the type of fuel
Fine tuning may be required if the chain saw, after changing
the type of fuel, performs differently with regard to starting,
acceleration, maximum speed, etc.
Conditions
• Before any adjustments are made the air filter should be
clean and the cylinder cover fitted. Adjusting the
carburettor while a dirty air filter is in use will result in a
leaner mixture next time the filter is cleaned. This can give
rise to serious engine damage.
• Do not attempt to adjust the L and H jets beyond either
stop as this could cause damage.
• Now start the machine according to the starting
instructions and let it warm up for 10 minutes. CAUTION!
If the chain rotates while idling the T-screw must be
turned anti-clockwise until the chain stops.
• Place the machine on a flat surface so that the bar points
away from you and so that the bar and chain do not come
into contact with the surface or other objects.
Low speed jet L
Turn the low speed jet L clockwise until it stops. If the engine
accelerates poorly or idles unevenly, turn the low speed jet L
anticlockwise until good acceleration and idling are achieved.
CAUTION! If the chain rotates while idling the T-screw
must be turned anti-clockwise until the chain stops.
Fine adjustment of the idle speed T
Adjust the idle speed with the T-screw. If it is necessary to re-
adjust, turn the T-screw clockwise while the engine is running,
until the chain starts to rotate. Then turn anti-clockwise until
the chain stops. When the idle speed is correctly adjusted the